The present invention relates to passive infrared motion detectors of the type used, for example, in residential lighting fixtures to illuminate a walkway or driveway when a person or automobile approaches. The invention is more particularly directed to various aspects of the electronics for controlling the operation of the motion detector including among other aspects electronic circuitry providing a variety of modes of operation for the motion detector and lighting fixture.
An early form of automatic lighting intended for outdoor use was controlled by a photocell that responds to the presence of daylight to automatically distinguish night from day. This form of lighting comes on at nightfall and remains on all night long until the light of dawn falls on the photocell to signal the arrival of day and trigger the nighttime lighting to be turned off. Such lighting has come to be known as dusk-to-dawn lighting. Another form of automatic lighting is motion-activated lighting governed by a passive infrared (PIR) motion detector. This form of lighting comes on when an infrared-emitting target such as a person or an automobile moves in the field of view of the motion detector. When such lighting was first introduced, it operated in a mode commonly known as security mode, in which the light remains off until motion is detected and then comes on for a pre-set period, typically about 15 minutes, in response to the motion. The light is then automatically extinguished if no further motion is detected for the pre-set period.
In a parallel development lighting fixtures providing background illumination at a low level have long been used in landscape and architectural design to focus attention on such features as walkways and garden paths, trees and prominent shrubbery, statuary and garden art, and ornamental building elements. Such lighting is commonly referred to as accent lighting and typically provides illumination at levels significantly less than full brightness. Motion-activated lighting was later combined with accent lighting to provide a motion-activated lighting apparatus in which the light comes on automatically at nightfall at an intermediate, accent lighting level and then when motion is detected, comes on at full brightness in response to the motion. When no motion is detected for the pre-set period, the light returns to the accent level. This mode of motion-detector operation has come to be known as accent mode.
Some PIR motion-activated lighting fixtures can be operated in more than one mode. U.S. Pat. No. 5,598,066 of Wiesemann et al. discloses a motion-activated lighting apparatus that can be operated in either security mode or in accent mode. The apparatus includes a switch by which the user can select the desired mode. U.S. Pat. No. 6,225,748 of Evans et al. discloses a motion-activated lighting apparatus in which the background lighting level can be continuously adjusted from full bright through intermediate levels suitable for accent lighting to no background lighting at all. When the user selects full bright, the apparatus operates in dusk-to-dawn mode. When the user selects no background lighting, the apparatus operates in traditional security mode. For mid-range selections the apparatus operates in accent mode with adjustable accent level.
Some PIR motion detectors, including those of the above U.S. Pat. Nos. 5,598,066 and 6,225,748, provide a manual override feature by which the user can completely bypass the normal mode of operation and manually turn on the light at its full brightness level regardless of whether the unit was set to operate in security mode or accent mode. The user typically toggles a wall switch controlling power to the lighting fixture to disable the normal mode of operation, whatever it may be, and energize the light at its full brightness level.